The present disclosure relates to a platform for carrying loads built from cellular confinement systems, also known as geocells. In particular, such platforms can carry high static, transitory, or vibratory loads. The present disclosure also relates to the components of such platforms and methods for making and using such platforms.
A cellular confinement system (CCS) is an array of containment cells resembling a “honeycomb” structure that is filled with infill, which can be cohesionless soil, sand, gravel, or any other type of aggregate. Also known as geocells, CCSs are used in applications to prevent erosion or provide lateral support, such as gravity retaining walls for soil, alternatives for sandbag walls, and for roadway and railway foundations. CCSs differ from geogrids or geotextiles in that geogrids/geotextiles are generally flat (i.e., two-dimensional) and used as planar reinforcement, whereas CCSs are three-dimensional structures with internal force vectors acting within each cell against all the walls.
The amount of load which a particular location can bear depends on the strength of the soil at that location. Soil is any material found in the earth at a locality, which may comprise of naturally derived solids including organic matter, liquids (primarily water), fine to coarse-grained rocks and minerals, and gases (air). The liquids and gases occupy the voids between the solid particles. The packing of soil is known as densification and is achieved during construction by compaction. Compaction is the process in which high load is temporarily applied to the soil by mechanical means such as a roller. When soil is compacted, the solid particles are forced closer together, reducing the volume in the voids that is occupied by air.
Dense soil is rather strong under compression, but has little to no strength under tension. When granular soil is compacted to a dense state, as is required in proper construction, it will reach its peak shear strength under compressive stresses at rather low compressive strain—usually at 1 to 3% strain. However, at larger strains, it will quickly reach lower shear strength than its peak as it undergoes through a strain-softening phenomenon. As a result, even dense soils may bear load poorly.
Geocells have been used in roadway and railway foundations. For example, the traditional method of creating a base for such foundations on poor load-bearing soils involves over-excavating, then filling with imported material that bears the load well. However, this method requires that the poor load-bearing soil be disposed of. One supplier of geocells, Geocell Systems Inc., notes that using an 8-inch thick geocell layer with sand infill can provide load-bearing strength comparable to a thicker rock-filled base layer, saving on costs. Presto, another provider of geocells, also describes their use as load support systems. However, these uses both require the export of undesired soil as well. These two examples are also based on polyethylene (PE) geocells, which are relatively weak and soft and tend to creep during usage. Consequently, the contribution of such geocells to soil confinement and/or reinforcement under sustained load is limited.
It would be desirable to provide improved geocell systems that are economical, stiff, strong, and support high sustained loads while reducing or preventing the need to export native soil elsewhere.